Pressure-relieving method and apparatus for autoclaves and the like



Nov. 25, 1930. T. GRISWOLD. JR 1,783,163

PRESSURE RELIEVING METHOD AND APPARATUS FOR AUTOCLAVES AND THE LIKE Filed Sept. 26 1925 I NVEN TOR.

727027146 rzlsw 0/67, f/

ATTORNEY.

Patented Nov. 25, 1930 UNITED STATES PATENT orrlcs THOMAS GRISWOLD, JR, OF MIDLAND, MICHIGAN, ASSIGNOR TO THE DOW CHEMICAL COMPANY OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN PRESSURE-RELIEVING METHOD AND APPARATUS FOR AUTOCLAVES AND THE LIKE Application filed September 26, 1925. Serial No. 58,804.

In the practical conduct of the treatment of fluids where it is required to releasefluid from a high to a lower pressure, difliculty is experienced with the release or throttling device or valve, which may beused. Particularly is this true if the drop in pressure through the valve is great and also if the fluid is hot or carries abrading material in suspension. The difliculty is one of corrosion or pitting, scouring, cutting, etc. of the valve and valve seat destroying same, interfering with the pressure reducing control and requiring renewals of valves or parts, which, in some cases, are very expensive. In certain cases the volume of fluid flow may be very small and an attempt to throttle such a flow may be likened to an attempt to wire draw a leak. This is. a very diflicult thing to do successfully, particularly with high pressures and high temperatures. I

Theobject of the present invention is to provide a method of throttling a fluid stream so as to reduce the drop in pressure of the current through a control orifice and in this way materially reduce, if not entirely eliminate, the destructive action of such stream or current on the control valve and associated parts. To the accomplishment of the foregoing and related ends, the invention, then, consists of the steps and means hereinafter fully described and particularly pointed out in the claims, the annexed drawing and the following description setting forth in detail certain means and one mode of carrying out the invention,.such disclosed means and mode illustrating, however, but one of various ways in which the principle of the invention may be used.

In said annexed drawing Fig. 1 illustrates one form of apparatus adapted for carrying out my present improved method, such apparatus being shown as interposed between a typical autoclave and a vessel into which the contents of such autoclave require to be discharged; Fig. 2 is a sectional view, on a somewhat larger scale,

of a modified form of apparatus designed for use in a similar connection; and Fig. 3 illus- 50 trates diagrammatically a -layout of pressure relieving elements arran ed to form a system whereby the pressure 0 a fluid at elevated temperatures and subject to vaporizat on may be reduced in whole or in part at the temperatures involved and whereby the release of such fluid may be efl'ected at varymg rates.

Fig. 1 illustrates a simple application of the present improved method and a corresponding simple form of apparatus, the latter being designed to discharge the contents of an autoclave 1 into a receiving tank 2. The fluid is relieved and led from the autoclave by way of pipe 3 through a control valve 4 and a long pipe or expansion coil 5. A second valve 6 may be placed between the coil and the receiver 2 and the latter will desirably be provided with a vent 7 and The bore of, pipe 5 and its length are chosen to suit the requirements in hand in such a way that the frictionof the fluid in passing through such pipe is suflicient to retard its velocity and restrict the volume of flow tothe desired amount subject to some control of valve 4. Where the fluid is discharged directly from such valve into the receiver 2, the pressure drop across the valve would be approximately equal to the difference between the pressure in the latter and that in autoclave l, and in some cases such difference is so great as to make it practically impossible to control the discharge by a valve or, at any rate, the use of a valve is both expensive and laborious because it has to be operated with a very small opening through which the fluid escapes at a very high velocity, producing scouring pitting and cutting.

I The eflect of the coil or tube 5, however, is to absorb this pressure change and permit such control valve to be operated in a more open position and hence with a wider range of operative throttling movement. If the pressure reducing coil is of suflicient'capacity, such valve may be operated practically wide open, while if scour occurs in the pres-- sure reducing pipe so as to decrease its frictional resistance and thereby lower the drop in pressure for the desired flow, the valve 4 will begin to close and function to maintain the pressure at such a point as may be desired, and to this'end, such valve may be made to operate automatically by any of several well known methods.

It is permissible to place the control valve in the position of valve 6 (shown as a manually controlled valve) or to have both valves operate automatically.

If a very long or conduit tube is required in order adequately to reduce the pressure, it will be conveniently coiled into a small bulk, as indicated in Fig. 1, and in place of such tube, a labyrinthine conduit or equivalent device, such as illustrated in Fig. 2, may be employed. This modified device comprises a tube 10 in which is placed a series of balls 11 or equivalent obstructions that nearly fill the bore of the tube and so are adapted intermittently to restrict the flow of a fluid through said tube while at the same time providing between the successive constrictions room for expansion or retarding of flow.

In the case of the simple arrangement of apparatus illustrated in Fig. 1, it will be understood that the tube 10 will be substituted for the pipe 5, and it will be noted that in the form shown in Fig. 2, the flow through said tube is from left to right, the balls 11 being held therein by means of a screen 12 adjacent the discharge end.

As previously indicated, in Fig. 3 is shown a modified arrangement of apparatus adapt-- ed to reduce pressure of fluids at elevated temperatures and subject to vaporization in whole or in part at the temperatures involved. This apparatus also provides a modified method of controlling the release of such fluids or of any fluids at varying rates as may be desired.

The processed or treated fluid under pressure and at an elevated temperature is designed to enter the system through the supply pipe or line 15 whence it passes through the header 16 in one or the other of a plurality of branches 17 that lead therefrom to a second header 18. Included in each such branch 17 is a throttle valve 19 that is protected on either side by a stop valve 20. In operation, but one or at least less than all of the valves in said branches are open to flow at one time, the others being held in reserve. When any particular branch 17 is to be put into use, it is desirable first to open the stop valves at either side of the particular throttle valve concerned and then to control the rate of flow as may be required with such throttle valve only, thusleaving the stop valves undamaged for use in entirely checkingthe flow when desired since this might be impossible with the throttle valve alone due to wear or cutting of the latter. When both stop valves in any such branch are thus closed, it is also possible to remove the interposed throttle valve for repair or replacement, the valves in one of the parallel branches 17 being thereupon opened so as to permit continuous operation of the pressure reducing step even while a Worn valve is being thus replaced or repaired.

From header 18 the fluid is passed through the coil 21 which, as illustrated, is a pressure reducing coil of the type illustrated in Fig. 1, but which may be a labyrinth of the type illustrated in Fig. 2 or an equivalent pressure reducing flow passage. Such coil may be heat insulated by means of an enclosing jacket 22 if desired. A series of tap lines 23 lead ofl from said coil' at various points in its length, such tap lines being joined to a header 24 and each being controlled by a throttle valve 25 with stop valves 26 on either side thereof, just as in the case of the branches 17 that connect headers 16 and 18. By means of these taps, the passage of the fluid flow may be permitted through the entire pressure reducing coil or labyrinth 21 or only a part thereof as may be desired.

If the fluid is cold and no vapor is to be conserved, the header 24 may be discharged directly by way of a pipe 27 into a receiver 28, but if at the temperature involved, vaporization takes place when pressure is reduced, preliminary separation may be made in a vapor separator 29 that drains through a cooler 30 into said receiver 28 and the hot yapor may then be condensed in whole orm part in a condenser 31 that drains into another receiver 32, the non-condensed vapors or gases being allowed to escape to waste or other use through a vent 33.

If a hot fluid be released through the apparatus just described, partial vaporization will occur with reduction of pressure provided the temperature is high enough. In such case, the volume of flow in the pressure reducing device 21 will increase with such vaporization and such increased volume Will require less length of tube or a less number of restrictions satisfactorily to reduce the pressure in the apparatus to a point where the control valves 19 in the branches 17 of the supply line, or the corresponding valves 25 in the taps 23 to the discharge line, will satisfactorily throttle the flow and maintam a constant and desired pressure in the apparatus in advance of the header 16. Just as in the case of the simpler form of apparatus illustrated in Fig. 1, these control or throttling valves 19 and 25, either one or the other, or both, may be automatically controlled if desired.

The general layout of elements arranged as shown in Fig. 3 also permits in certain processes of the economic use of the heat in a processed liquid to evaporate a portion of the same and thus save heat which would otherw1se.be required if vaporization were necessary in the process. There is also proylded a method of separating such liquid 1nto two or more constituents by means of the mechanical separator and condenser provlded for the vapor, as described above. If the condenser be worked to condense all the vapor, two fractions are obviously secure whlle if it be worked to condense only a part of such vapor, a third fraction will leave through the vent 33 and if of value may of course be recovered by being separately condensed. This principle of opera tion may be elaborated upon to any desired degree by the interposition of additional condensers and separators, as will be readily understood.

In releasing a hot fluid it may alternatively be first cooled under pressure by interposition of a cooler in the flow aheadof the pressure reducing device, or devices, without affecting the principle of my invention.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the means and the steps herein disclosed, provided those stated by any of the followmg claims or their equivalent be employed.

I therefore particularly point out and distinctly claim as my invention 1. A method of discharging a high pressure fluid from an autoclave, which comprises releasing such high pressure fluid through an orifice. and simultaneously retarding the rate of flow thereof by causing the fluid stream to traverse a constricted passageway of suf ficient length to absorb by frictional resistance a material portion of thetotal pressure drop, whereby destructive actionupon such orifice is reduced.

2. A method of releasing fluid from a higher to a lower pressure, which comprises controlling the rate of release by a controlled orifice responsive to such higher pressure, and progressively lowering the pressure of the fluid by passing-it through an extended passageway offering resistance to flow therethrough in amount suflicient to limit the pressure drop in. the controlledorifice to a minor fraction of the total pressure drop.

3. In apparatus of the character described, means forcontrollingthe withdrawal of a fluid under high pressure from a container, said means comprising a valve and a passage oflering high resistance to absorb a large portion of the pressure drop.

:1. In apparatus of the character described, the combination of an autoclave, valve means for controlling the Volume of a fluid stream passing from such autoclave, and means other than a valve for reducing the destructive action-at said valve means by opposing resistance in an extended passageway.

5. In apparatusof the character described, the combination of an autoclave, valve means for controlling the volume of the fluid stream passing from such autoclave, and means other than a valve to provide a suflicient resistance in the path of flow of such stream to materially absorb pressure drop, whereby destructive action on the valve is inhibited.

6. In apparatus of the character described,

the cqmbination of an autoclave, valve means for controlling the volume of a fluid stream passing from such autoclave, and means for reducing the destructive action at such valve, said means including a pressure-drop absorbing labyrinthine passageway.

7. In apparatus of the character the-combination of an autoclave, valve means for controlling the volume of a fluid stream passing from such autoclave, and means for reducing the destructive action at such valve, said means including a pressure-drop absorbing adjustable passageway.

8. In apparatus of the character described, the combination of an autoclave, a branched discharge line, a control valve in each of the branches of said line, a stop valve on either side of each said control valve, and an extended passageway opposing straight-direction flow communicable with said branches.

9. In pressure relieving apparatus for autoclaves and the like, the combination of a branched discharge line, a control valve in each of the branches of said line, two stop valves in each .such branch, one on each side of the corresponding control valve, and a described,

header connecting such branches beyond said valves and leading to the discharge.

10. In pressure relieving apparatus for autoclaves and the like, the combination of a branched discharge line,a control valve in each of the branches of said line, two stop valves in each such branch, one on each side of the corresponding control valve, a header connecting such branches beyond said valves, and a duct leading from said header and including a portion arranged and constructed to interpose resistance to the flow of the fluid therethrough, whereby a substantial portion of the drop in pressure is absorbed.

11. In pressure relieving apparatus for autoclaves and the like, the combination of a branched discharge line, a control valve in each of the branches of said line, two stop valves in each such br'anch, one on each side of the corresponding control valve, a header connecting such branches beyond such valves, a duct leading from saidheader and including a portion arranged and constructed to interpose resistance to the flow of the fluid therethrough, whereby a substantial portion of the drop in pressure is absorbed, and a plurality of taps connected with said duct at diflerent distances from said header.

Signed by me this 23rd day of September, 

